1. Technical Field of the Invention
The present invention relates to an inspection method and device for inspecting electrodes of electronic components, lands on a printed circuit board substrate, or the condition of cream solder printed on the lands by means of a screen printing apparatus or the like.
2. Description of Related Art
For production of electronic circuit boards, various types of electronic components 2-4 are mounted on a printed circuit board substrate as shown in FIG. 3. Such components include, for example, a ball grid array (BGA) type chip 2 in which a multiplicity of electrodes are arranged in a matrix fashion, a quad flat package (QFP) type chip 3 in which a multiplicity of electrodes are projected on four sides thereof, and small out-line package (SOP) type chip 4 with electrodes on both sides thereof. For bonding these components 2-4, lands 5-7 are preliminarily formed on the substrate, and cream solder is printed in register with these lands 5-7 with the use of a screen printing apparatus as shown in FIGS. 4A and 4B.
A screen 8 has apertures 9-11 at positions corresponding to each of the lands 5-7. A camera 12 is provided for taking images of the cream solder printed on the lands 5-7 on the substrate 1. The images are then processed for the purpose of inspection. The camera 12 is constructed to be movable in X and Y directions. Each of the positions of the lands 5-7 to be inspected is designated in advance to the camera, so that the camera moves automatically from one land to the other in succession for inspecting the lands. The camera 12 is connected to a video monitor, with which the image taken by the camera 12 is shown on the display.
Camera teaching of inspection positions is carried out as described below with reference to FIG. 8 and FIG. 9. At step 1 (#1), a group of lands for mounting an electronic component to be inspected is selected. At step 2 (#2), an operator moves the camera while monitoring the position of the camera on the video monitor 13 to a position where the lands 5-7 to be inspected can be seen in the video monitor 13. The number of lands which will fit in the screen of the video monitor, or, the number of lands within the field of view of the inspection screen provided by the camera 12 is limited as shown in FIG. 9 because of the resolution of the camera 12. Accordingly, after designating the initial inspection position, if it is judged at step 3 (#3) that there is a next inspection position to be designated, the procedure returns to step 2, and the next inspection position is designated by moving the camera 12 in a similar manner as described above. The foregoing operation is repeated until inspection positions for all of the lands have been designated.
For example, in the case of BGA type chip 2, each of the nine inspection positions arranged in a matrix fashion as shown in FIG. 9A are designated to the camera by positioning the camera at each of the inspection positions one after another. In the case of QFP type chip 3, each of the twelve inspection positions surrounding the perimeter of the component in a rectangular fashion as shown in FIG. 9B are designated to the camera one after another. Such camera teaching of the inspection positions is necessary for all of the lands 5-7 corresponding to all of electrodes on the electronic components 2-4 to be mounted on the substrate. Moreover, such camera teaching is done for inspection of both lands 5-7 on the substrate 1 and apertures 9-11 in the screen 8.
However, there are quite a large number of lands for bonding electrodes of electronic components especially of the types mentioned above such as BGA, QFP, and SOP. Therefore, teaching of the inspection positions, or the position of the camera which determines the field of view 14 of the inspection screen, takes time as it entails positioning of the camera at each of the inspection positions, with attendant loss in production.
In view of the foregoing, an object of the present invention is to provide an inspection method and device, with which teaching operation of inspection positions for the camera to perform land inspection is simplified with enhancement in operation efficiency.
To accomplish the above object, the present invention provides an inspection method for inspecting electrodes of electronic components or lands formed on a circuit board substrate corresponding to the electrodes of the electronic components to be mounted on the circuit board substrate, comprising the steps of: teaching an inspection starting point to a camera by positioning the camera at the inspection starting point where a predetermined number of electrodes or lands come within a field of view of the camera; and moving the field of view of the camera automatically in succession along a predetermined path corresponding to the shape of the electronic component from the inspection starting point to an inspection end point by a preset algorithm.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.